We have had this house and pool a little over three years. When we got it, the previous owners were using Home Depot puck and granulated chlorine. Not knowing better, I continued to use the exact same stuff. Sometimes I would also dump liquid chlorine (from home Depot) in trying to get the chlorine level to stay up (it did not work).
3in tablets (trichloro-s-triazinetrione 99%) in a Rainbow Lifegard in line automatic feeder (after filter and heater). (over 70lbs in three years).
Quick disolving chlorinating granules sanitizer and shock (Sodium dichloro-s-triazinetrione dihydrate 99%) scattered in pool. (over 400lbs in three years)
I started looking around online after fighting with green algee non stop for the last year. It seems no matter how much chlorine I dump in the pool, it is gone within 24 hours and it won't keep the algee down. I have put 4 quarts of Algicide 50% (see below) in the pool in the last three years, and there was an empty bottle of it here when we purchased the house, so I suspect at least 5 quarts have been put in the pool, possibly more. I can't keep the algee away for more than three days during the summer, more than ten days in the winter.
After trying to lower the TA as detected by my 5 way home depot test kit for the last month using the lower ph, areate pool, repeat method, (successfully lowered from 350 to 240 as measured by that test kit then stalled and would not lower any more) I purchased the TF-100 test kit. I ran the CH test two times to make sure I didn't make a mistake and got 1300 both times. I ran the CYA test once with straight pool water and the liquid didn't even make it 1/4 the way from the bottom of the sight tube to the 100 mark before I couldn't see the dot, so I diluted the pool water with 3 parts distilled water and ran the test again, it made it about 2/3 of the way up the sight tube from the bottom to the 100 mark before it was impossible to see the dot. By measuring the tube on both readings and calculating, I am guessing my CYA is just over 600, I am sure it is well over 400. Using OTO to test, I got my chlorine to 3.0 using bottle bleach at dark last night, this morning an hour after sunrise, it was zero.
pH = 6.8
FC = 0
TC = 0
TA = 220
CH = 1300
CYA = 400+
Temp = 74
At least 5 quarts of Pool Time Algicide 50% since last fill
((n-alkyl (C14, 60%; C16, 30%; C12, 5%; C18, 5%) dimethyl benzyl ammonium chloride 49.8%; n-dialkyl (C14, 60%; C16, 30%; C12,5%; C18, 5%) methyl benzyl ammonium chloride 0.2%))
TA = 200
CH = 210
My question is: Is there any way to resolve the chemical problems I seem to be in without draining at least 90% of the water out of the pool? And, until I can drain and fill the pool (might be a few months), what chlorine level do I need to reach to shock the pool, and what level should I be keeping the chlorine at?